The present invention concerns the reduction of the blister phenomenon that occurs in automotive tires, particularly in automobile racing tires. More particularly, the invention presents a system and method for preparing a racing tire to prevent the occurrence of blistering.
The typical automotive tire is formed of galvanized rubber. During the molding of the tire, air or other compressible gases frequently become trapped within the rubber. Moreover, in tires utilizing reinforcing plies, gas can become trapped between layers of material in the tire.
During the manufacture of the tire, the heat and pressure of the vulcanization process can cause the gas to expand within the rubber. This expansion may be sufficiently strong to separate layers of the tire, or result in blisters, either internally or on the surface of the tire. It can be readily appreciated that these blisters represent a weak area in the tire that is susceptible to failure during use. For instance, tires with defects of this nature are more susceptible to chunking, in which pieces of the tread are torn out of the tire. This problem is particularly acute with racing tires. Not only does the chunking effect disrupt the effectiveness of the tire, it can also make the tire more susceptible to blowouts while the racing vehicle is being operated at high speeds.
Many tire manufacturing processes have been developed to reduce the quantity of gas trapped within the tire rubber. The cost many of these processes are prohibitive. Moreover, no known system is 100% effective. Thus, most tires include some volume of gas retained within the tire. In many cases, unless a defect arises during the manufacturing process, the gas retained within the body of the tire will go unnoticed and will usually cause no significant problems.
However, in the field of automobile racing, the typical racing tire is exposed to significant temperatures and loads during a race. Blisters and chunking occur with regularity in racing tires of all types. Asphalt tires typically have a fairly high durometer, ranging between 100-150. Even with this high degree of hardness, the extreme heat increases the risk of blistering. As the racing tires subjected to the high temperatures and loads, the entrapped gas tends to migrate outward through the tire material. Once it reaches the surface or tread of the tire, the entrapped gas manifests itself as a blister. This blister can cause create a tire vibration, cause the tire to loose traction, or lead to the destruction of the tire.
The same phenomenon occurs in dirt track racing tires. These tires generally run cooler than asphalt tires. However, dirt track tires are considerably softer than asphalt tires, having a durometer ranging between 30-80. Thus, the combination of heat, load and a softer tire result in the same gas migration and blistering problem as experienced by the asphalt racing tires.
Thus far, there are no known systems or techniques that reduce the risk of tire blistering due to gases trapped within the tire material. Instead, most of the development in the field of racing tires has been to reduce the temperature of the tire or to manipulate the tread pattern to minimize the likelihood of the chunking phenomenon. In the latter case, varieties of tread block designs have been developed, with varying degrees of success in reducing chunking. However, none of the tread design approaches eliminates the problem of gas entrapped within the tire material.
In the realm of cooling the tire, one well known approach has been to form or remove a large diameter plug from within each tread block of the tire. The theory behind this approach is that the plug hole provides a path for conducting heat from the interior of the tire. In addition, the plug holes provide increased surface area for heat dissipation. This approach has found little success for asphalt racing tires, and has thus been generally limited to dirt track tires. However, due to the soft nature of the tire, the excessive size of the plug holes tends to distort the tread block when the weight of the car is applied at that location. This results in undue distortion of the tire at the tread block, which can ulitimately increases the risk of chunking.
In another approach, a tool, such as a sharpened socket or tire sipe, is used to cut a pattern into the tire tread. Significant problems arise with this approach, since the tool would frequently cut too deeply into the tire. Thus, many tires processed in this way became unbalanced, flatted or self-destructed due to separation of the tire cords or core from the tread blocks.
There remains a significant need in the field of automotive tires, particularly racing tires, for a system and technique to reduce blistering. The need is particularly great for a system and method to account for gas trapped within the tire rubber.
The invention contemplates a device and technique for processing tires that provides an escape path for gas trapped within the tire during the manufacturing process. In one aspect of the invention, the tire is penetrated by a multiplicity of pinholes dispersed about the tread surface. The pinholes are sufficiently shallow so as not to disturb the integrity of the tire. Moreover, the diameter of the holes is very small so hundreds or thousands of pinholes can be provided around the circumference of the tire without significantly affecting the surface area of the tire tread and gripping surface.
The pattern of pinholes provides a ready path for gas to escape from the tire. Thus, as the tire is heated during use, such as racing, gas entrapped within the body of the tire gradually migrates radially outward as a gas bubble. As the bubble approaches the tread surface, it contacts a plurality of pinholes and gradually dissipates through these holes to exit the tire. The pinholes are thus sized to effectively allow passage of a gas bubble therethrough.
The present invention contemplates a device for preparing a tire, such as a racing tire, on-site. In one embodiment, a support frame is configured to rotatably support a vehicle tire. A tire preparation element is provided that includes a plurality of spikes or pins configured to smoothly penetrate the tire rubber. In one feature, the spikes can be heated to facilitate penetration of the tire material, particularly high durometer materials.
In one embodiment, the tire preparation element includes at least one, and preferably, two drums rotatably supported on the frame. An array of spikes project radially outward from each drum. In one specific embodiment, the drums are spaced apart to support the tire in a vertical orientation. In this specific embodiment, the weight of the tire drives the tire down onto the spikes. The tire can be manually rotated, or one of the spiked drums can be rotated to thereby rotate the tire.
In another specific embodiment, means for rotating the tire is provided. In one form, this means includes a drive roller that frictionally engages the tire. The drive roller can be provided with a manual crank to rotate the roller and thereby rotate the tire. As the tire rotates, pinholes are formed in the tread surface by the spiked drum(s). In one version of this embodiment, the drive roller is disposed between two spiked drums. In another version, a spiked drum and the drive roller are disposed apart to support the tire in a vertical orientation.
In certain embodiments of the invention, an axle is connected to the support frame and configured to rotatably support the tire. The position of the axle can be adjusted to accommodate different radius tires and to maintain adequate pressure between the tire and the spiked drum(s). In the preferred embodiment, the tire is mounted vertically on the device so gravity assists in maintaining the adequate. Alternatively, the support frame can allow the tire to be mounted horizontally, provided the spikes of the drum can fully penetrate tread surface.
In another embodiment of the invention, a plate is provided onto which the tire can be rolled or driven. The plate includes a multiplicity of spikes projecting upward therefrom, each spike configured to penetrate the tire material. In one aspect of this embodiment, the array of spikes has a width approximating the width of the tire and a length corresponding to the circumference of the tire. Thus, pinholes can be created around the entire tread surface of the tire by one pass of the tire over the support plate. In one specific embodiment, the support plate can be hinged so it can be folded up when not in use.
In certain embodiments of the invention, the spikes or pins can be heated to facilitate penetration of the tire material. Thus, in one embodiment, the spiked drums can be heated. In another embodiment, a heating element can be mounted within the support plate. In this embodiment, the heating element can be in conductive contact with the plurality of spikes so that each spike is individually heated.
One benefit of the present invention is that the array of pinholes within the tire provide an escape for virtually all gas trapped within the tire during manufacture. Another benefit is that the gas escape paths are provided without compromising the strength, integrity or performance of the tire, even during the high load and temperature environment of asphalt or dirt racing.
Yet another benefit resides in features of the invention that make the device for preparing tires portable and easy to use on-site. Thus, the present invention provides a device that can be used to prepare any tire from any source.
One object of the invention is to provide an automotive and racing tire that is less susceptible to blistering and virtually immune to the problems normally associated with gas entrapped within the tire material. Another object is achieved by features of the invention that make it readily adaptable as a portable device or as an initial manufacturing process.
Other objects and benefits of the present invention will become apparent from the following written description and accompanying figures.